Hi there. Thanks for looking.
Do you know anything about the new chunk API 1.13.2 events?
No? Nor does the below plugin it seems!

This tiny but powerful plugin I have used for ages is called OrePlus.https://dev.bukkit.org/projects/oreplus
This plugin was made in Jan 5, 2013 for MC CB 1.4.6-R0.3!!!
Worked perfectly right up to MC 1.12.2 *claps*

Works pasively with other world generators. OrePlus is an automatic block replacer/populator.
It does it instantly as the world generates, block by block. Without ever skipping any blocks.
The plugin is faaaaast! No skips. Even during a TPS intensive WorldBorder plugin flood fill, giant replace list.It just takes block type A and replaces it with block type B. Or adds a block type in ore like formations.
Can do different blocks in a per biomes list. Setable with height limit values and or a % chance.

Example uses.
All deserts automatically generate with red sand. All Badlands would have white sand and no red.
Add, remove or replace ores in per biome list.
All trees in jungles have birch logs instead with facing varients replaced perfectly.
Replace entire world's ocean sea level water with packed ice, eye level 62 water with ice in ocean biomes.
Find every lava block below eye level 20 and automatically replace it with obsidian in high hills biomes.
Attempt to replace every block type in all villages in deserts with a list of quartz replace blocks, stairs etc.
Replace in all jungle biomes that are not hill type jungles, all vines with air.
Cause all mineshafts to have no rails. Iron bars instead of fenceposts.
Mossy cobblestone not in the biomes it naturally spawns in (EI Dungeon floors) generates as emerald ore.
Replace all id 31:1 (short grass) in plains with mix of all flower ids instead.
Entirely flood the world's caves below eye level 40, replace all air with water in rivers/oceans.
More uses.. so many more Tiny plugin. Just needs 1.13+ compatibility tweak.
Once the user's config is done they would get worldborder plugin or something
to generate the entire world within the defined border radius. Done. Sweet!

This thing worked great up to MC version 1.12.2.
Sadly now it throws massive console fits in 1.13.2 (Paper, latest version)https://pastebin.com/gxch2PBR <- Fits. Big ones. Timeout. Crash server.MC 1.13+ desperately needs an ore/block populator that is also block type replacer.
MC 1.13+ has dire low ore population density per chunk. A plugin like this would fix it and so much more.
OrePlus is a gem of a plugin but has long been abandoned. Works perfectly up to 1.12.2.

This plugin needs rebuilt or replicated for 1.13+

The open source of the plugin could be updated to carry on with the new 1.13 chunk loading info.https://github.com/jaquadro/OrePlus^ For Inspiration... Last version is just 14.05 KB